One of Fergie's major policies in deciding line-ups over his time is that the Back 4 has always been constant. The midfield and attacking structures are variable, but the back 4 has always been there. However, with the extreme lack of defensive numbers, and only 2 fit defenders travelling to Germany, it's possible that a Back 3 might have to be enforced, which would struggle to cope with Dzeko, Grafite, Misimovic and possibly Obafemi Martins.
Maybe our best option is to go for a back 4, and play Fletcher at Right Back and Carrick at Centre Back, similar to our setup against West Ham. This would mean that Carrick would partner Oliver Gill at CB, while Evra would be the only recognisable defender in the back 4, at Left Back.
Perhaps a 5-3-2 with 2 Wing Backs is our best option. This could work effectively if Evra and Park Ji-Sung play as Wing Backs, while Fletcher, Gill and Carrick take the 3 Central Defensive positions. Gibson could also possibly be tried as a Centre Back in place of Fletcher.
Whilst it's a shame that Ritchie De Laet is ineligible to play, as he would certainly have fitted into this squad given the circumstances, it is still possible for us to come up with an effective makeshift defensive structure. Having said that though, our lack of fit players is concerning.